My Home Ideas

Special Offers

Be the first to know about This Old House contests, sweepstakes, and events and receive special offers and promotions from your favorite home improvement brands. We'll even send you regular reminders to enter our sweepstakes.

If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

Recirculating Pump & Cold Water

I am having to replace my water heater. As with most people I have a long wait to get hot water to my kitchen sink. I am looking at installing a recirculating pump. Most I see are retrofit where a sensor/valve is connected to the cold water line under the sink to finish the loop. Wouldn't that mean that your cold water isn't as cold as it was and wouldn't I have to wait until the cold water starts coming back?

With the retrofit kits, can you install a return line directly to the hot water heater instead of the cold water return? Would it use the same equipment?

Re: Recirculating Pump & Cold Water

Do you have a brand name? Most commercial buildings have a third line for HW return from the farthest points. It has a small 1/6-1/50 HP pump controlled from a thermostat on the returning line which puts the water back into the HW heater tank. When the stat sees the water return temp at 90 or so, it shuts off the pump as it is no longer needed.
What you are talking about reminds me of the home I lived in 40 years ago. It was a very long building with a water heater and bath at one end and a bath at the other end. Ther was both a hot and cold water line going to the bellows valve below the tank. The bellows had the valve open when it was cold but whenever the toilet was flushed, it would use water from the hot line until it warmed up to about 70 degrees. The advantage of this was that it also kept the tank from sweating. I didn't think they were still made.

Re: Recirculating Pump & Cold Water

The only pump I know of is at lowes or home depot, the pump is a watts. The pump is set up on a timer, not a thermostat...

It is made to use the cold water supply as the return loop for the pump, not a seperate line. With that setup I would think that the cold water won't be as cold.

If I use the pump and put a dedicated return line at the end of the run (kitchen sink to HW heater), I am assuming there needs to be a valve either at the sink or before the HW intake. THis would be needed so you don't send good HW back to the tank or create a siphon effect due to the cold water entering the tank.

The other question I have is that if I lose electric, I am assuming that water won't go through the pump, you would need a bypass?

Re: Recirculating Pump & Cold Water

I just looked further into this and there is a temperature sensative valve that gets installed under the sink.

They say to connect it to the cold water supply, but if I install a Tee where by CW enters the HW heater and run that up to the kitchen sink, then I am mimicking a CW supply and I should just be able to cap the outflow of the valve.

Re: Recirculating Pump & Cold Water

I was not sure what you were referring to earlier.
In a typical system with a pump, you have a normal size hw supply line to the faucet as in a normally plumbed house. In addition, there is a small 1/2" return line piped into a tee on the hw supply to that faucet. This small line is the return line and it is piped into the suction side of the pump, which is back at the heater. The discharge side of the pump goes through a check valve (to prevent reverse flow when the pump is off etc.) and then into a tee on cw line into the heater. There is also a thermostat sensor on the line at the pump to shut off the pump when the returning water is around 80 degrees meaning there is hot water at the faucet and it is just wasting water to keep running. You also should have a valve on either side of the pump to make it easier to remove for repair.

My other reference was about a thermostatic valve that would provide a similar benefit without the use of electricity.

The one you are looking at has the full flow of hot water going through the pump at all times, and you would still have hw if the pump was not running. I am not familiar with this system, but it looks like it would work well and have two added benefits. First, you do not have to run a return line under the house. Second, you can put the sensor valves on several faucets if you have several areas where you need hot water quicker. Here is an explanation of the valve.

Multiple sensor valves may be installed on a branched hot water system. The sensor valve is a thermostatically controlled valve that begins to open/close at 98 degrees +/- 5 degrees. When the Recirculating Pump is set to run, the valve allows the cold water in the hot water supply line to "by-pass" into the cold water supply line. When the hot water reaches the sensor valve, it heats the plug (the thermal sensor) inside, which shuts the valve, leaving hot water sitting at the fixture, and no cold water down the drain

Re: Recirculating Pump & Cold Water

ZZZ has excellent info & relevant posts on this topic & his advice should be followed.

I just wonder if I could add a few points that may or may not be relevant.

1) if you're going to move the HWH anyway, why not move it to a point directly below the bath/kitchen piping so the HW has less distance to travel--insulating the pipes may be all that is needed to keep the water hot.

2) hot water in a pipe will move by convection if there is a return loop back to the HWH; in other words, if the HW supply pipe is angled always upwards to the fixtures, the HW will circulate all by itself to the fixtures & thus be there when a faucet is opened; this is due to the lighter density of HW compared to the heavier density of CW.

If it works, it would eliminate the expense of the kit & installation/labor.

Re: Recirculating Pump & Cold Water

don't use the kits from lowes or the depot. The proper way that a good service plumber would add a domestic recirc line would be to run a third line from the fatrhest fiture back to the drain on the tank. remove the boiler drain from the bottom of the tank, install a BRASS T, put the boiler drin into the end of the t and the third line into the top of the t. add a short peice of pipe and then a check valve to prevent the cold water in the bottom of the tank from backflowing when the pump is off. then onstall your pump on the third line with the flow arrow pointing in the appropriate direction. as for a choice of pumps you deffinatley need to use either an all bronze or stainless steel pump. I would recommend the Taco 004 or the groundfus equivelent. be prepared for the pump to cost $350-$450 the pump should run continuosly, but if you want you could install a tep control on the return line

Re: Recirculating Pump & Cold Water

I am not familiar with the 004 Taco, but I would definitely use a Taco 00 series wet rotor pump. The smallest one should do in most cases. You should be able to buy a 003 model for about $170. I don't believe anyone makes a better pump for the money.

Re: Recirculating Pump & Cold Water

What would be the best way for me to do a similar hot water recurculating system? The bathroom sink takes forever to get hot water to it.

I have just replumbed my basement using PEX. I have manifolds for the hot and cold systems and I have added a new electric water heater. I too do not seam too impreassed with the new plastic valves on the HWH.